The present invention relates to safety interlock systems for lawn mowers and more particularly relates to electrical ignition interlock systems for walk-behind lawn mowers.
Walk-behind lawn mowers normally include a blade housing having a discharge opening, which may be closed by a door for mulching operation or which may have discharge or bagging chutes inserted therein respectively, when it is desired to direct material onto the ground before it recirculates through the housing or when it is desired to direct material to a bag mounted to receive material impelled through the bagging chute.
In order to ensure that the mower will not be operated without the discharge opening being closed by a door or cover or without some sort of chute being associated with the opening, some known designs have included a door pivotally mounted on the housing along one edge of the opening and spring biased toward a closed position over the opening. Also provided is an electrical ignition interlock system including a normally closed kill switch which grounds out the engine ignition. The kill switch is located such that it is held open either by the door when the latter is closed or by the bagging attachment when the latter is in place. U.S. Pat. No. 4,043,102 issued to Uhlinger et al on Aug. 23, 1977 discloses a mower design of the type just described.
One disadvantage of electrical ignition interlock systems of the aforedescribed type is that the switch may somehow stick in the open position which would permit operation of the mower with the discharge opening uncovered and disassociated with any type of chute.